Electric-circuit protector



S. N. BARUCH. ELECTRIC CIRCUIT PROTECTOR. APPLICATION FILED APR.12.1915.

76 INVENTOR.

PatentedSept. 7, 1920,

5. N. EF/PUC'H II 71V [535155.- a: 41 7%) BY fiw 0%? ATTORNEY.

UNITED..STATES- PATENT OFFICE.

SYDNEY N. BARUCH, or sue FRANCISCO, CALIFORNIA, ASSIGNOB TO BABUCHELECTRIC commoner. conrom'nox, or sea FRANCISCO, camro mm, 4 conronuzonor 414110 314.

ELECTRIC-CIRCUIT PROTECTOR.

1,352,044. p c fiee ieiie Ileittersl'atent- Patented SephV,

Application flled' April 12, 1915. Serial 170. 20,756.

tions surrounding said wire, 1'. e., if the wire To all whom it mayconcern:

is so placed that the escape of heat there- Be it known that I, SYDNEYN. BARUCH,

a citizen of the United States, residing at San Francisco, in the countyof San F rancisco, State of California, have invented a new and usefulElectric-Circuit Protector, of which the following is a specification insuch full and clear term as will enable those skilled in the art toconstruct and use the same.

This invention relates to a thermo protector for electric apparatusespecially illustrated with a three phase motor. It is applicable to anyelectric circuit.

This invention relates to a modified form of the apparatus shown anddescribed in In United States Patent No. 1,281,482, dated October 15,1918, and its object is to produce an apparatus which will operate witha smaller time factor than that shown in the aforesaid application.

It is commonly known to those skilled in the art that when a three phasemotor starts up it takes several times its normal full load runningcurrent or amperage and should an attempt be made to start the motorwith one fuse out leaving but a single phase in circuit with the motor,it would continue to take several times its normal running currentwithout-starting up. The temperature produced by this overload currentwould destroy the insulation on the conductors of the motor. Likewise,should the motor be runningand one of the fuses be blown out after themotor has started either in the primary or secondary circuits the motorperhaps if a large one would continue to run but would take through thesingle phase in circuit twice its normal full load current capacity andalso burn out.

An object of this invention is to provide a device which will operate toopen the circuit of an electric motor or other apparatus, when thecurrent in said circuit reaches a value which is deleterious to thewinding of .the motor or other apparatus.

Another object of the invention is to provide an apparatus which isoperated by the heating effect of the current in an electric circuit toopen said circuit when the temperature of apparatus in the circuitapproaches a deleterious temperature.

The heating characteristics of a wirepassing current are determined bythe condifrom is retarded or reduced its carrying capacity is reduced inthe same proportion and vice versa. In a motor the heat is dissipated bythe air currents, the frame of the motor, etc. With the presentapparatus the electrical conductor is installed in an insulated chamberso that the heat is retained therein keeping the apparatus at slightlyhigher temperature than the motor with which its winding is in series.In order to protect a three phase, an Edison three wire system, or twophase three wire system, two elements are used in order to get full protection and on all single circuits only one element is used. The devicemay be used to set ofl an alarm or to cut off the current altogether asmay be desired.

An embodiment of the invention is shown in the drawing in which the samereference numeral is applied to the same portion throughout, but I amaware that there may be many modifications thereof.

Figure 1 is a diagrammatic view of a three wire electric circuit havingthis cutting out apparatus applied thereto,

ig. 2 is a side elevation of the switch illustrated in Fig. 4,

Fig. 3 is a vertical sectional view of this cutting out apparatus,

Fig. 4 is a sectional view of a slightly modified form of cutting outapparatus in which a mechanical trigger is used in the place of theelectrical releasing device illustrated in Figs. 1 to 3 inclusive, and

Fig. 5 is a diagrammatic front elevation of a switch with a no voltagerelease control.

This invention seeks to make use of theexpansion of a wire which itselffurnishes the mechanical means for operating the cutting out apparatus.

In the figures the numeral 1 indicates the generator having suitablewires extending to the fuses, 2, 3 and 4 from which fuses the wires 5, 6and 7 extend to the contact plates 8, 9 and 10, which plates'are mountedon the common form of switch block-11. At the bottom of the switch block11 there is a plurality of cars 12, 13 and 14 of a common form for thesupport of the pivoted knives 15, 16 and 17 which form the means forconnecting' the circuits. These knives are connected at their upper endsby the cross bar 18 and have an operating handle 19. The cross bar 18extends to one side of the knife 17 and it is locked in the givenposition by means of aswinging latch 20 pivoted to the block 11 at 21.Springs 22, 23 and 21 are used which normally disengage the knife it thelatch 20 is raised and this latch is raised by energizing the magnet 25by sendingcurrent through the circuit wires 26. 26 and 27, the lattertwo of which are connected with the binding posts 28 and 29 on theprotective apparatu 30 and 31. The wire 26 is connected with the centerof the coil 25 while the wires 26 and 27 are connected to opposite endsthereof. The wire 26 is connected with the wire 33 and the wires 31 and35 pass into the bottom of the protective devices and out at the top toconnect with the switch knives.

The protective apparatus comprises a porcelain tube 30 having metal caps36 at opposite ends. The wire 34: passes through the two metal caps andis soldered or otherwise permanently secured to each of them, said wirealso passing through a hole in a spring 37. The spring 37 is secured tothe inside v of the porcelain tube at 38 and in its normal position itwould contact with a set screw 39 secured in the side of the porcelaintube 30, but which wire is pulled up tight enough to prevent it fromtouching the set screw 39, unless the heat due to the current passingtherethrough should slacken it sufficiently to allow the spring 37 to.touch said set screw 39.-

Tn order to accumulate some of theheat in the wire itself the wire iscovered with asbestos insulation 40 and 41 which tends to retain some ofthe heat and thereby increase the expansion.

In operation whenever the load on the motor M becomes too great and thequantity of current passing is heavy enough to cause the wire 34 withinthe casing 30 to relax enough to permit the spring 37 to touch the setscrew 39 a current will pass through the magnet 25 and the armature 42will be drawn up rapidly enough to cause the latch 20 to be disengagedfrom the cross bar 18 thereby allowing the springs to push the switchknives out of contact and break the circuit.

In Fig. 4 there is shown a slightly modified form of the invention inwhich the porcelain tube is indicated at 50, said tube having metal caps51 and 52 through which the wire '53 extends. This wire is covered withasbestos or other heat retaining material 54; and 55 and a spring 56 issecured within the porcelain tube 57 while the wire prevents said springfrom bearing upon the plug 58. The tube supports a suitable clampedbracket 58 having a depending portion 59 which bracket has a spring 60secured thereto bearing on a small pawl 61,

which pawl is adapted to engage a hook 62 at the upper end of a rod 63on which is wound a spiral spring 64.

The rod 53 is pivotedto a latch 65 and tends to cause it to bedisengaged from the cross bar 67 of the knife switch 68, said switchbeing pushed normally out of contact by means of the spring 69.

In this form of the invention the heat accumulating in the tube andinsulation causes the wire 53 to expand whereupon the spring 56 pushesthe fiber block 58 outwardly and thereby disengages the hook 61 andallows the spring 61 to push down on the latch 65 thereby releasing theswitch, provided the current is heavier than that allowed for in theadjustment of the device.

In the form of theinvention shown in Fig. 5, 70 indicates the switchblock on which are mounted the terminals 71 to 74 to which the wires 75to 78 are connected. The switch blades 79 and 80 are pivotally connectedto the terminals 71 and 72 in a well known manner, a bar 81 connectingthem at the top. Springs 82 and 83 tend to hold the switch open while alatch 84 on the lower end of the armature 85 locks the switch closed.The armature is normally pulled down by the spring 86 while the magnet87 holds the armature up when energized.

In this case the protective apparatus 88 takes its current through awire 89, resistance R, wire 90 and wire 91, the heat generated beingsufficient to allow the spring 92 to close the connection with thecontact screw 93 and wire 91 leading to the coil 87 from which wire 95leads to thewire 91.

When the system shown in Fig. 5 is to be used the switch is closed andheld closed by hand for a teivmoments whereupon the magnet 87 will beenergized and the switch will be locked, but should the current go offfor a long enough time to allow the wire inside the protective apparatusto break the connection with the contact screw 93 the switch will bereleased by the latch 84. A suitable resistance R is used to makecertain that the coil receives enough current to energize it.

Having thus described my invention what T claim as new and desire tosecure by Letters Patent of the United States, is as follows,modifications within the scope of the claims being expressly reserved:

1. A device for releasably holding a switch in an electric circuit inthe closed position, comprising a rigid casing, a metallicconductoranchored at its ends and disposed within said casing, saidconductor being in said circuit and being adapted to be heated bycurrent therein, a spring bearing against said conductor intermediateits ends and tending to flex said conductor, and means actuated by thespring upon a predetermined 130 flexing of the conductor to release saidswitch.

2. A device for releasably holding a switch in an electric circuit inthe closed position, comprising means engaging the switch for holding itclosed, a plunger operative to release said holding means, a conductorin said circuit adapted to be heated in proportion to the current flowin said circuit and a spring bearing against said conductor intermediateits ends and tending to flex said conductor, the spring operating on apredetermined llexure of the conductor to contact with and move theplunger to release the holding device.

3. A device for releasably. holding a switch in an electric circuit inthe closed position, comprising a casing, a conductor in said casinganchored at its ends and disposed in said circuit whereby it is heatedby the current therein, heat insulating casings surrounding theconduc'tor adjacent its ends, a

spring engaging the conductor intermediate the casings and tending toflex it transversely in one direction and means adapted to be engaged byswitch.

4. A device for releasably holding a switch in an electric circuit'inclosed position, comprising means for holding the switch closed, aflexible conductor in the circuit adapted to be heated by currenttherein, and means for flexing the conductor in one direction operasaidspring to release the tive upon a predetermined flexure of saidconductor for releasing said holding means. In testimony whereof I havehereunto set my hand this 5th day of April, A. D. 1915, in the presenceof the two subscribed witnesses.

SYDNEY N. BARUCH.

Witnesses:

C. P. GRIFFIN, L. H. ANDERSON.

